fix: regression on multisite canonical URLs (v4)

[therealpecus]

Fixes #469.

Changes proposed in this pull request:

• fixes an issue introduced with 4.2.2 on multisite installations where the language prefix in canonical URLs was repeated

This PR applies to v4 of the plugin.

[niektenhoopen]

@Tam Would you be able to have a look at this? The canonicals are now incorrect on all 4.2.2 installations.

[niektenhoopen]

@Tam Any updates????

[MytiX]

@Tam Could you please provide us with information about a possible future merge of the pull request ? @therealpecus This works perfectly 👍🏻

[Tam]

Thanks!